Timepieces of this type are known in the prior art in particular from patent documents CH-627 042, CH-666 980 and EP-0195 742. The last two documents describe timepieces which include several coaxial display elements, each bearing one or several marks which simulate stars describing orbits around the center. In the second document, the center represents the sun and the marks simulate planets, while in the third document the center represents the earth and the moving elements simulate the relative displacements of the sun, of the celestial vault or of the moon relative to the earth.
The driving mechanisms for these different display elements include gear trains, the different wheel sets of which are permanently engaged with one another and are driven in a continuous manner from the hours wheel.
The ratios are such that the duration of the sidereal periods represented: the year, moon phases, etc. are exact with very high precision.
As has been indicated in patent document CH-666 980, timepieces conceived in this manner may not be constructed in order to simulate the epicycloidal displacement of the moon around the earth with the sun as center. Effectively, in this case the complication of the gear trains would require a volume of the timepiece which is not compatible with the dimensions of a portable timepiece.